Effects of Interferon-α,β,and γ on the Function of Differentiated Leukemic HL-60 Cells Induced by 1,25-Dihydroxyvitamin D 3

The differentiation of HL-60, a human leukemic cell line, into monocyte-like cells (D₃-HL-60 cells) is induced by 1,25-dihydroxyvitamin D₃ (D₃). We examined the effects of interferon (IFN) treatment of D₃-HL-60 cells on the expression of cell surface antigens, the phagocytic activity for fluorescent beads, production of oxygen radicals, and intracellular growth of Legionella pneumophila. Activation of D₃-HL-60 cells with IFN-γ, β, and α for 24 h significantly increased expression of CD16, CD36, CD71, and HLA-DR antigens. IFN-γ markedly enhanced the phagocytic activity of beads in D₃-HL-60 cells. There was no significant difference in phagocytic activity between cells exposed to IFN-α or β and untreated D₃-HL-60 cells. IFN-α, β, and γ enhanced production of oxygen radicals, including superoxide, by D₃-HL-60 cells. Superoxide production was enhanced to the greatest degree by IFN-γ, followed by IFN-β and then IFN-γ. Intracellular growth of L. pneumophila in D₃-HL-60 cells was inhibited by interferons (IFN-γ > β> γ). Similar results were obtained in human mononuclear cells. These data indicate that interferons can act as biologic response modifiers not only in human mononuclear cells but also in differentiated leukemic cells. Our results may have implications for the development of differentiation therapy for treatment of leukemia.